Certain hexahydrodibenzopyranones have recently been found to be useful in the treatment of anxiety, depression, and analgesia; see U.S. Pat. Nos. 3,928,598, 3,944,673 and 3,953,603. Of particular importance among such compounds are the 1-hydroxy-3-substituted-6,6-dimethyl-6,6a,7,8,10,10a-hexahydro-9H-dibenzo[ b,d]pyran-9-ones, especially the 6a,10a-trans isomers which are somewhat more active pharmacologically than the corresponding 6a,10a-cis isomers. The prior art preparation of such 6a,10a-trans-hexahydrodibenzopyranones suffers from being multistep and of low overall yields; see Fahrenholtz, Lurie and Kierstead, J. Am. Chem. Soc. 88, 2079 (1966), 89, 5934 (1967). A new synthesis of 6a,10a-trans-hexahydrodibenzopyranones has recently been discovered which involves reaction of the corresponding 6a,10a-cis isomer with an aluminum halide to effect complete epimerization to provide exclusively the 6a,10a-trans isomer. Such epimerization process is the subject of Blanchard and Ryan's co-pending application Ser. No. 702,807 filed July 6, 1976, now U.S. Pat. No. 4,054,582. It has also been recently discovered that cis-1-hydroxy-3-substituted-6,6-dimethyl-6,6a,7,8,10,10a-hexahydro-9H-dibe nzo[b,d]pyran-9-ones are readily prepared in one step by reaction of a 1-alkoxy-4-(1-hydroxy-1-methylethyl)-1,4-cyclohexadiene with a 5-substituted resorcinol in the presence of a catalyst such as boron tribromide, boron trifluoride or stannic chloride. Such condensation reaction is the subject of Day and Lavagnino's co-pending application filed this even date herewith.
An object of this invention is to provide an improvement in the above-referenced process for preparing dl-cis-1-hydroxy-3-substituted-6,6-dimethyl-6,6a,7,8,10,10a-hexahydro-9H-d ibenzo[b,d]pyran-9-ones from 5-substituted resorcinols and 1-alkoxy-4-(1-hydroxy-1-methylethyl)-1,4-cyclohexadienes.